Breakdown of GHG emissions from agriculture in the United States 2021, by segment
Enteric fermentation was the largest source of greenhouse gas emissions in the U.S. agriculture sector in 2021, with a share of 39 percent of total emissions (excluding energy emissions). Enteric fermentation is a part of the digestive process in ruminant animals and produces large amounts of methane, a potent greenhouse gas. Livestock manure (mainly from cattle) is the second-largest source of agriculture-related GHG emissions in the U.S.
